Hands-On: The Tecno Spark Slim Proves An Ultra-Thin Phone Could Actually Be Good [Gallery]

I don’t understand the whole “ultra-thin” phone trend. It just seems… kind of dumb? And it sounds like 9to5 readers largely agree. But at MWC 2025, I was pleasantly surprised by the Tecno Spark Slim.

Ahead of MWC, Tecno teased the Spark Slim as the “industry’s slimmest phone.” The 5.75mm device won’t break records, as the mostly-forgotten Moto Z was much thinner at just 5.2mm, but it does something that the Moto Z, and the upcoming Galaxy S25 Edge, didn’t, and that’s to have a sizeable battery.

2016’s Moto Z had a tiny 2,600 mAh battery inside, extremely small even a near-decade ago. Now, the Galaxy S25 Edge is expected to have a 3,900 mAh battery, which is very small by modern standards.

The Tecno Spark Slim, just a concept for now, promises to get around this with a 5,200 mAh silicon-carbon battery, bigger than some of even Samsung’s full-thickness flagship phones. That alone means I’m pretty okay with an ultra-thin device, but I still didn’t fully understand the appeal, until I held it.

Tecno’s Spark Slim has an incredibly thin design that’s also incredibly light. It almost doesn’t feel real, and Tecno even mentioned at MWC that it had to add weight to the device to help avoid that. At 166g, though, it still feels unbelievable. The hardware is also very polished and feels great in the hand with its curves. The LED-equipped camera bar is neat too, and gives some Nexus 6P vibes until it lights up. My only real complaint boiled down to the buttons, which were somehow a bad kind of clicky and mushy at the same time.

Again, this is only a concept for now, and there’s no word on Tecno creating a device that matches this same design or even hits the same level of thinness. I’m still not sold on thin phones, but Tecno just proved to me that it’s possible to do it “right.”

What do you think?